utf8reader.java

derby database source code.good for you.

/*

   Derby - Class org.apache.derby.impl.jdbc.UTF8Reader

   Copyright 2004 The Apache Software Foundation or its licensors, as applicable.

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.

 */

package org.apache.derby.impl.jdbc;

import java.io.InputStream;
import java.io.Reader;
import java.io.IOException;
import java.io.UTFDataFormatException;
import java.io.EOFException;
import java.sql.SQLException;

/**
*/
public final class UTF8Reader extends Reader
{

	private InputStream in;
	private final long         utfLen;	// bytes
	private long        utfCount;		// bytes
	private long		readerCharCount; // characters
	private long		maxFieldSize;	// characeters

	private char[]		buffer = new char[8 * 1024];
	private int			charactersInBuffer;	// within buffer
	private int			readPositionInBuffer;

	private boolean		noMoreReads;

    // maintain a reference to the parent object so that it can't get 
    // garbage collected until we are done with the stream.
    private ConnectionChild      parent;

	public UTF8Reader(
    InputStream in,
	long maxFieldSize,
    ConnectionChild      parent,
	Object synchronization) 
        throws IOException
	{
		super(synchronization);

		this.in     = in;
		this.maxFieldSize = maxFieldSize;
		this.parent = parent;

		synchronized (lock) {
			this.utfLen = readUnsignedShort();
		}
	}

	/*
	** Reader implemention.
	*/
	public int read() throws IOException
	{
		synchronized (lock) {

			// check if closed..
			if (noMoreReads)
				throw new IOException();

			if (readPositionInBuffer >= charactersInBuffer) {
				if (fillBuffer()) {
					return -1;
				}
				readPositionInBuffer = 0;
			}

			return buffer[readPositionInBuffer++];
		}
	}

	public int read(char[] cbuf, int off, int len) throws IOException
	{
		synchronized (lock) {
			// check if closed..
			if (noMoreReads)
				throw new IOException();

			if (readPositionInBuffer >= charactersInBuffer) {
				if (fillBuffer()) {
					return -1;
				}
				readPositionInBuffer = 0;
			}

			int remainingInBuffer = charactersInBuffer - readPositionInBuffer;

			if (len > remainingInBuffer)
				len = remainingInBuffer;

			System.arraycopy(buffer, readPositionInBuffer, cbuf, off, len);
			readPositionInBuffer += len;

			return len;
		}
	}

	public long skip(long len) throws IOException {
		synchronized (lock) {
			// check if closed..
			if (noMoreReads)
				throw new IOException();

			if (readPositionInBuffer >= charactersInBuffer) {
				// do somthing
				if (fillBuffer()) {
					return -1;
				}
				readPositionInBuffer = 0;
			}

			int remainingInBuffer = charactersInBuffer - readPositionInBuffer;

			if (len > remainingInBuffer)
				len = remainingInBuffer;

			readPositionInBuffer += len;

			return len;
		}

	}

	public void close()
	{
		synchronized (lock) {
			closeIn();
			parent  = null;
			noMoreReads = true;
		}
	}

	/*
	** Methods just for Cloudscape's JDBC driver
	*/

	public int readInto(StringBuffer sb, int len) throws IOException {

		synchronized (lock) {
			if (readPositionInBuffer >= charactersInBuffer) {
				if (fillBuffer()) {
					return -1;
				}
				readPositionInBuffer = 0;
			}

			int remainingInBuffer = charactersInBuffer - readPositionInBuffer;

			if (len > remainingInBuffer)
				len = remainingInBuffer;
			sb.append(buffer, readPositionInBuffer, len);

			readPositionInBuffer += len;

			return len;
		}
	}
	int readAsciiInto(byte[] abuf, int off, int len) throws IOException {

		synchronized (lock) {
			if (readPositionInBuffer >= charactersInBuffer) {
				if (fillBuffer()) {
					return -1;
				}
				readPositionInBuffer = 0;
			}

			int remainingInBuffer = charactersInBuffer - readPositionInBuffer;

			if (len > remainingInBuffer)
				len = remainingInBuffer;

			char[] lbuffer = buffer;
			for (int i = 0; i < len; i++) {
				char c = lbuffer[readPositionInBuffer + i];
				byte cb;
				if (c <= 255)
					cb = (byte) c;
				else
					cb = (byte) '?'; // Question mark - out of range character.

				abuf[off + i] = cb;
			}

			readPositionInBuffer += len;

			return len;
		}
	}

	/*
	** internal implementation
	*/


	private void closeIn() {
		if (in != null) {
			try {
				in.close();
			} catch (IOException ioe) {
			} finally {
				in = null;
			}
		}
	}
	private IOException utfFormatException(String s) {
		noMoreReads = true;
		closeIn();
		return new UTFDataFormatException(s);
	}

	private IOException utfFormatException() {
		noMoreReads = true;
		closeIn();
		return new UTFDataFormatException();
	}

	/**
		Fill the buffer, return true if eof has been reached.
	*/
	private boolean fillBuffer() throws IOException
	{
		if (in == null)
			return true;

		charactersInBuffer = 0;

		try {
		try {
		
			parent.setupContextStack();

readChars:
		while (
				(charactersInBuffer < buffer.length) &&
			    ((utfCount < utfLen) || (utfLen == 0)) &&
				((maxFieldSize == 0) || (readerCharCount < maxFieldSize))
			  )
		{
			int c = in.read();
			if (c == -1) {
				if (utfLen == 0) {
					closeIn();
					break readChars;
				}
				throw utfFormatException();
			}

			int finalChar;
			switch (c >> 4) { 
				case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7:
					// 0xxxxxxx
					utfCount++;
					finalChar = c;
					break;

				case 12: case 13:
					{
					// 110x xxxx   10xx xxxx
					utfCount += 2;
					int char2 = in.read();
					if (char2 == -1)
						throw utfFormatException();

					if ((char2 & 0xC0) != 0x80)
						throw utfFormatException();		  
					finalChar = (((c & 0x1F) << 6) | (char2 & 0x3F));
					break;
					}

				case 14:
					{
					// 1110 xxxx  10xx xxxx  10xx xxxx
					utfCount += 3;
					int char2 = in.read();
					int char3 = in.read();
					if (char2 == -1 || char3 == -1)
						throw utfFormatException();

					if ((c == 0xE0) && (char2 == 0) && (char3 == 0))
					{
						if (utfLen == 0) {
							// we reached the end of a long string,
							// that was terminated with
							// (11100000, 00000000, 00000000)
							closeIn();
							break readChars;
						}
						throw utfFormatException();
					}

					if (((char2 & 0xC0) != 0x80) || ((char3 & 0xC0) != 0x80))
						throw utfFormatException();	

					finalChar = (((c & 0x0F) << 12) |
							   ((char2 & 0x3F) << 6) |
							   ((char3 & 0x3F) << 0));
					}
					break;

				default:
					// 10xx xxxx,  1111 xxxx
					throw utfFormatException();		  
			}

			buffer[charactersInBuffer++] = (char) finalChar;
			readerCharCount++;
		}
		if (utfLen != 0 && utfCount > utfLen) 
			throw utfFormatException("utfCount " + utfCount + " utfLen " + utfLen);		  

		if (charactersInBuffer != 0)
			return false;

		closeIn();
		return true;
		} finally {
			parent.restoreContextStack();
		}
		} catch (SQLException sqle) {
			throw new IOException(sqle.getSQLState() + ":" + sqle.getMessage());
		}
	}


	// this method came from java.io.DataInputStream
    private final int readUnsignedShort() throws IOException {
		int ch1 = in.read();
		int ch2 = in.read();
		if ((ch1 | ch2) < 0)
			throw new EOFException();

		return (ch1 << 8) + (ch2 << 0);
	}
}